Semiconductor-on-insulator (SOI) technology, which represents an advance over traditional bulk silicon processes, was first commercialized in the late 1990s. The defining characteristic of SOI technology is that the semiconductor region in which circuitry is formed is isolated from the bulk substrate by an electrically insulating layer. One advantage of isolating circuitry from the bulk substrate is a dramatic decrease in parasitic capacitance which allows access to a more desirable power-speed performance horizon. Therefore, SOI structures are particularly appealing for high frequency applications such as radio frequency (RF) communication circuits. As consumer demand continues to tighten the power constraints faced by RF communication circuits, SOI technology continues to grow in importance.
A typical SOI structure 100 is shown in FIG. 1. The SOI structure 100 includes a substrate layer 101, an insulator layer 102, and an active layer 103. The substrate layer 101 is typically a semiconductor material such as silicon. The insulator layer 102 is a dielectric which is often silicon dioxide formed through the oxidation of the substrate layer 101 in situations where the substrate layer 101 is silicon. The active layer 103 includes an active device layer and a metallization or metal interconnect layer, and further includes a combination of dopants, dielectrics, polysilicon, metal wiring, passivation, and other layers, materials or components that are present after circuitry has been formed therein. The circuitry may include metal wiring 104 (e.g. in the metal interconnect layer); passive devices such as resistors, capacitors, and inductors; and active devices such as a transistor (e.g. in the active device layer).
RF transistors operate on signals that are biased at large signal bias voltage and that vary from the bias voltage according to a signal voltage. Both values can swing dramatically. As a result, the switches produce electromagnetic noise 105 that propagates through the semiconductor device. In particular, the electromagnetic noise can interact with substrate 101 and result in nonlinear distortions in the signal voltage.